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How to Select the Right Type of HVAC Filter

Keeping the filter changed in your HVAC system is a critical maintenance step. The benefits include better air quality, reduced fire hazards, and improved system efficiency. Running an HVAC system with a dirty filter puts an unnecessary amount of stress on the unit which shortens its life and increases maintenance costs. Here are some useful tips to help you select the right filter for your HVAC unit.

Manufacturer Guidelines

The easiest place to find the filter requirements is the manufacturer’s label on the HVAC unit or the owner’s manual. The manufacturer’s label is typically found on the side of the unit or behind the main access panel. Look for information related to the size and type of filter that the manufacturer recommends. These guidelines will help you determine which filter will allow the unit to run at the optimal efficiency.

Filter Size

The most important piece of information that you need is the correct filter size. If the filter is too large, it won’t fit in the HVAC unit. If the filter is too small, the air will not be filtered properly. You have a few options if you can’t locate the recommended filter size.

 

Option 1 - Remove the existing filter and look for the size printed on the side of the filter.

 

Option 2 - If the printed dimensions aren’t visible, use a measuring tape to check the height, width, and depth of the filter.

 

Option 3 - If the filter is missing, measure the opening where the filter would normally go. Use caution using this method as a bad measurement will result in purchasing the incorrect size.

 

It is important to note that filters will have both an actual size and a nominal size. The actual size is the physical dimensions of the filter. The nominal size is the dimensions rounded up to the nearest inch. This is used to make the dimensions easy to market and organize in the store. For example, a filter that has physical dimensions of 19-⅞” x 19-⅞” will have a nominal size of 20” x 20”.

MERV Rating

Once you have determined the correct size, you will need to decide on the quality of filtration. HVAC filters are assigned a rating based on how efficient the filter is at capturing particles out of the air.

 

Each filter receives a score called a MERV rating (Minimum Efficiency Reporting Values). The MERV rating is a system used by the American Society for Heating, Refrigeration, and Air-Conditioning Engineers.

 

The MERV rating scale runs from 1 to 20. Filters with higher MERV ratings are more effective at filtering out smaller particles such as viruses, smoke, and fine dust. Lower ratings are less effective and only capture larger particles such as hair, pollen, and dust mites.

 

Keep in mind that higher MERV ratings are not always better. While higher score filters minimize the contaminants that will pass through the filter, they also reduce airflow and forces the unit to work harder. This can shorten the life of the HVAC unit and increase maintenance costs. Always select a filter that has a MERV rating that aligns with the manufacturer’s recommendations.

Disposable or Washable Filters

In some cases, you may have the option to select a disposable or washable filter for your HVAC unit. There are pros and cons to both types.

 

Washable filters are great because they only have to be purchased once. They can be removed, washed, and reinstalled over and over. This is great for the environment and is a cheaper option. The only tradeoff is that washable filters typically have a much lower MERV rating.

 

Disposable filters are more common but must be thrown away when they are dirty. While they are available with higher MERV ratings, they are not environmentally friendly and cost more over the life of the HVAC unit.